Composition for use in coating



2,855,323 Patented Oct. 7, 1958 COMPOSITION FOR USE IN COATHYG VINY LITE NEGATIV ES Nathan B. Hughes, Berwyn Heights, Md.

No Drawing. Application July 13, 1955 Serial No. 521,881

The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon, in accordance with the provisions of 35 United States Code (1952) Section 266.

The present invention relates to surface coatings and particularly contemplates an improved protective and engravable coating to be used for the preparation of glass and plastic engraving plates. In accordance with the principles of the present invention a sheet of glass or plastic material is coated so as to provide a moisture-impervious surface, one which resists accidental scratching yet which permits the cutting of clean lines during the engraving process.

The present invention is a continuation in part of Applicants Copending Application, Serial No. 325,697 filed on December 12, 1953, now abandoned.

In the art of lithography sheets or plates of glass or plastic are employed which are carefully coated with an opaque surfacing material. Some available commercial surfacing materials employed for such purpose are identified as Floquil, Flopaque, or Scribecoat. All such materials form an opaque colored coating when applied to the surface of the sheet. During the process of photoengraving, an image of the material to be reproduced is projected on the surface of the engraving plate, and the engraver then engraves the outline of the image on such prepared surface by means of a suitable engraving tool. The resulting sheet having opaque and transparent portions then comprises an engraving plate or negative which is used in the subsequent photoengraving process.

It will be understood that for proper lithography, the surface of the plate must be opaque to light and must also be capable of being scribed to form clean lines or delineations. Presently known coatings suffer the disadvantage that they do not provide for clean lines when out with an engraving tool and accordingly tend to give blurred images. Moreover, when the coating is applied of proper density to act as a good negative material, the light ap plied during photo-reproduction has a tendency to burn through.

It is accordingly an immediate object of the present in vention to provide a liquid protective coating for application to materials to be used as engraving plates in photoengraving, for the purpose of preserving the original finish against normal wear, and to protect against further wear surfaces which already have become somewhat worn, and for other applicable purposes.

It is another object of the present invention to provide a surfacing composition for application to the surface of materials to be used as engraving plates in photoengraving which is sufiiciently opaque to the transmission of light for photographic purposes and yet which is readily cut by an engraving tool so as to form clean, well-defined lines.

Other uses and advantages of the invention will become apparent upon reference to the specification.

In the above-identified copending application, a coat ing material was described intended especially for protecting and improving the appearance of painted or lacquered surfaces, such as automobile body finishing. The present invention is directed to a coating material designed primarily for the application to the surfaces of engraving plates. The composition is provided in the form of a thin liquid which may be applied in one or more layers as desired, to form a coating. When dried it has a hard, glossy finish which acts not only to protect the surface of the engraving sheet, but to provide a readily engravable surface which, when cut by an engraving tool, provides a clean, well-defined line. The invention comprises a composition made up of castor oil, benzol, beeswax, and turpentine combined in accordance with the procedure outline in the following illustrative example.

Castor oil A 02. (4- drams). Benzol /2 oz.

Beeswax /2 oz. (225 grains). Redistilled turpentine 12 oz.

The beeswax is dissolved in heated turpentine and the castor oil is blended with the benzol. The two resulting solutions are mixed thoroughly. In use, the liquid solution made in accordance with the above-described procedure, is either brushed on or applied to the engraving plate with a cloth. Alternately the surface may be dipped or the liquid coating may be applied by pouring the liquid on the surface of the material to be coated and wiping off the excess. The coating is allowed to set or dry for a short time and then polished until smooth and glossy.

When the above-described composition is applied to an engraving sheet it renders it waterproof, scratch resistant, and improves its cutting quality. As a result, the engraver has much more freedom in his work. Accidental marring of the surface by being touched with water or perspiration is minimized and the resulting resistance to accidental scratching effects an obvious saving in time normally spent in retouch work. When used as an undercoating or substrata in connection with vinylite or vinyl acetate sheet material the coating provides a substantial saving in time and effort in forming the en.- graved surface. Specifically, the coating protects the plastic surface from penetration by the engraving tool thereby enabling corrections to be made by the process of recoating a particular area to provide a new engraving surface.

The coating also has a beneficial effect on the photo graphic process above alluded to forming a subsequent step in the lithography. Specifically, the coating makes a better lightproof surface insofar as negative material is concerned than known existing compositions. The composition of the present invention has a Baum reading of 20", which gives adequate protection from light in photographing a negative being processed.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made within the scope of invention as defined in the appended claims:

In the claims:

1. The method of making a composition for use in coating plastic negatives such as vinyl acetate comprising the steps of dissolving approximately .038 part by weight of beeswax in approximately .9 part by weight of turpentime by application of heat, dissolving approximately .019 part by weight of castor oil in approximately .038 part by weight of benzol and combining each of the solutions so formed.

2. The method of preparing plates of sheet material for photoengraving comprising preparing a composition consisting essentially of approximately .038 part by weight of beeswax, approximately .019 part by weight Ounces Castor oil A Benzol /2 Beeswax /2 Turpentine 12 4. An engraving plate suitable for use in photoengrav- 4 ing comprising a vinyl acetate sheet, one surface of said sheet being coated with a composition consisting essentially of approximately .038part by weight of beeswax, approximately .9 part by weight of turpentine, approximately .019 part by weight of castor oil, and approximately .038 part by weight of benzol.

References Cited in the file of this patent UNITED STATES PATENTS 1,398,600 Muths May 25, 1920 1,459,380 Tillyer June 19, 1923 1,492,698 Owen May 6, 1924, 1,992,010 Kittredge Feb. 19, 1935 15 2,048,303 Swartz July 21, 1936 

1. THE METHOD OF MAKING A COMPOSITION FOR USE IN COATING PLASTIC NEGATIVES SUCH AS VINYL ACETATE COMPRISING THE STEPS OF DISSOLVING APPROXIMATELY .038 PART BY WEIGHT OF BEESWAX IN APPROXIMATELY .9 PART BY WEIGHT OF TURPENTINE BY APPLICATION OF HEAT, DISSOLVING APPROXIMATELY .019 PART BY WEIGHT OF CASTOR OIL IN APPROXIMATELY .038 PART BY WEIGHT OF BENZOL AND COMBINING EACH OF THE SOLUTIONS SO FORMED. 